1. Field of the Invention
The present invention relates to a liquid processing apparatus and liquid processing method for performing a predetermined liquid process on a substrate, such as a semiconductor wafer.
2. Description of the Related Art
In the process of manufacturing semiconductor devices or flat panel display devices (FPD), liquid processes are frequently used, in which a process liquid is supplied onto a target substrate, such as a semiconductor wafer or glass substrate. For example, processes of this kind encompass a cleaning process for removing particles and/or contaminants deposited on a substrate, and a coating process for applying a photo-resist liquid or development liquid in a photolithography stage.
As a liquid processing apparatus used for this purpose, the following apparatus of the single-substrate processing type is known. Specifically, a substrate, such as a semiconductor wafer, is held on a spin chuck, and a process liquid is supplied onto the front surface or front and back surfaces of the wafer, while the wafer is rotated. Consequently, a liquid film is formed on the front surface or front and back surfaces of the wafer, thereby performing a process.
In general, an apparatus of this kind is arranged to supply a process liquid onto the center of a wafer, and rotate the wafer to spread the process liquid outward, thereby forming a liquid film and throwing off the process liquid. A surrounding member, such as a cup, is disposed around the wafer to guide downward the process liquid thrown off from the wafer, so that the process liquid is swiftly drained. However, where such a cup or the like is used, part of the process liquid may bounce back to the wafer as mist, and generate defects thereon, such as water marks and/or particles.
As a technique for preventing this problem, Jpn. Pat. Appln. KOKAI Publication No. 8-1064 discloses a technique which utilizes a process liquid receiving member to be rotated integrally with rotary support means that rotates along with a substrate held thereon in a horizontal state. The process liquid receiving member receives a process liquid scattered around the substrate, and guides the process liquid outward to collect it. According to this publication, the process liquid receiving member includes a horizontal eaves portion, an inclined guide portion for guiding the process liquid outward and downward, a horizontal guide portion for guiding the process liquid outward in the horizontal direction, and a wall portion extending upward in the vertical direction, in this order from the substrate side. With this arrangement, the process liquid is guided into a narrow space to prevent mist from bouncing back onto the substrate, while the process liquid is drained from a drain port formed at a corner of the process receiving member. The process liquid is then discharged through grooves extending outward within a spacer disposed around the process liquid receiving member.
In the case of the apparatus described above which utilizes a process liquid receiving member to be rotated integrally with rotary support means, drainage is radially discharged all around from the liquid receiving member due to the rotation thereof, and thus an annular drain cup needs to be disposed to receive the drainage. However, the annular drain cup thus disposed prolongs the time necessary for removing the drainage from the drain cup through a drain port, and thereby brings about the following problems particularly where process liquids of different kinds are employed.
i) In general, where process liquids of different kinds are employed, they are directed to separate drain passages by switching after use. However, if the time length is long from the time switching on the supply side is performed for each process liquid to the time the process liquid is discharged from a drain port, it becomes very difficult to find the timing of switching between drain passages.
ii) Even after switching on the supply side is performed for each process liquid, the former process liquid is still left in the drain cup. Consequently, these two process liquids of different kinds used before and after the switching therebetween are drained together in a mixed state.